Q: A cell uses the Na$^+$/K$^+$ pump to move ions across its membrane. Which equation best represents the direction of ion movement by this pump?

$3\ \mathrm{Na}^+_{\text{in}} \rightarrow 3\ \mathrm{Na}^+_{\text{out}}$ and $2\ \mathrm{K}^+_{\text{out}} \rightarrow 2\ \mathrm{K}^+_{\text{in}}$

Question 1

Which statement best describes the 'fluid' aspect of the fluid mosaic model of the plasma membrane?

Accepted Answer

Phospholipids and some proteins can move laterally within the layer, allowing flexibility.

Question 2

A red blood cell is placed in a hypertonic solution. What will happen to the cell, and why?

Accepted Answer

It will shrink because water leaves the cell to the area of higher solute concentration.

Question 3

Which of the following molecules is most likely to diffuse directly through the phospholipid bilayer without the help of a transport protein?

Accepted Answer

O$_2$

Question 4

What is the primary function of cholesterol in animal cell membranes?

Accepted Answer

It helps maintain membrane fluidity at different temperatures.

Question 5

Which type of membrane protein is most likely to function as a channel for facilitated diffusion?

Accepted Answer

Integral protein

Question 6

A cell uses the Na$^+$/K$^+$ pump to move ions across its membrane. Which equation best represents the direction of ion movement by this pump?

Accepted Answer

$3\ \mathrm{Na}^+_{	ext{in}} ightarrow 3\ \mathrm{Na}^+_{	ext{out}}$ and $2\ \mathrm{K}^+_{	ext{out}} ightarrow 2\ \mathrm{K}^+_{	ext{in}}$

Question 7

Which process requires cellular energy (ATP) to move substances across the plasma membrane?

Accepted Answer

Active transport

Question 8

Why do aquaporins increase the rate of water transport across cell membranes?

Accepted Answer

They form hydrophilic channels that allow water to bypass the hydrophobic core of the membrane.

Question 9

Which of the following best describes selective permeability of the plasma membrane?

Accepted Answer

The membrane allows some substances to cross more easily than others.

Question 10

A plant cell is placed in a hypotonic solution. What is the expected outcome?

Accepted Answer

The cell will become turgid as water enters the cell.

Question 11

Which factor would most likely increase the rate of diffusion across a cell membrane?

Accepted Answer

Increasing the concentration gradient

Question 12

Which of the following is NOT a function of membrane proteins?

Accepted Answer

Energy storage

Question 13

Which statement correctly differentiates between facilitated diffusion and active transport?

Accepted Answer

Facilitated diffusion does not require energy and moves substances down their concentration gradient, while active transport requires energy and moves substances against the gradient.

Question 14

Which of the following best explains why integral proteins remain embedded in the phospholipid bilayer?

Accepted Answer

Their hydrophobic regions interact with the hydrophobic core of the bilayer.

Question 15

Which process describes the movement of large particles into a cell by engulfing them in a vesicle?

Accepted Answer

Endocytosis

Question 16

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

It will remain the same size as there is no net movement of water.

Question 17

Which equation best represents the net movement of molecules during diffusion?

Accepted Answer

$	ext{Net movement}: 	ext{High concentration} ightarrow 	ext{Low concentration}$

Question 18

Which of the following is a real-life example of bulk transport in cells?

Accepted Answer

White blood cell engulfing a bacterium by endocytosis

Question 19

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the diffusion of water from an area of high water concentration to low water concentration.

Question 20

Which of the following would most likely decrease membrane fluidity in a cell exposed to cold temperatures?

Accepted Answer

Increasing the proportion of saturated fatty acids in phospholipids

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